The present invention relates to a process for producing a pipe section in a rotary mold drum, in which the pipe wall is formed by introducing liquid plastic, as well as fillers and/or reinforcing materials, accompanied by the formation of a material layer on the inner wall of the mold drum.
Considerable development has taken place in the production of tubular workpieces, in which no metallic materials are used. Various different construction stages are known and in connection with all of these it is assumed that at least one part is made from one or more plastic materials. Apart from pipeline parts made from a single plastic material and which can be produced without difficulty, e.g. with the aid of an extruder, production processes are known in connection with larger pipe diameter designs, in which the plastic if reinforced with additives. It is known to reinforce plastics for such pipe line parts by using fibrous materials of carbon, glass, boron, etc.
In the case of pipeline parts, particularly those having larger diameters, it is often desired that such parts have greater dimensional rigidity than can be achieved with plastic alone. Thus, it is known to reduce the flexibility of the plastic pipeline part by combining different types of material with the plastic, e.g. fibers (U.S. Pat. No. 4,171,626). In addition, building materials, e.g. moldings are known (DE-OS No. 2 352 384), which comprise several layers of different materials. For this purpose it is possible to use inorganic materials with corresponding binders, e.g. mortar or concrete. Although the moldings made from such materials have the desired dimensional rigidity, and the advantage also exists of these materials being generally less expensive than the suitable plastics, it is either not possible or only incompletely possible to achieve a reliable connection between the mortar or concrete and the plastic.
It is known in connection with the production of dimensionally rigid tubular parts from fiber reinforced plastic to use a rotary drum having the desired diameter and into which the plastic with the admixed fiber additives are introduced in the liquid state. The centrifugal action exerted by the charged plastic on rotating the drum leads to a uniform material distribution, so that a tubular material of uniform dimensional rigidity and strength is obtained. However, the amount of plastic required and consequently the costs of such tubular parts are high.